Electric smelting furnace



Jan. 15, 1924.

T. KAWA! ELECTRI C SMELT ING FURNACE Filed July 25 1919 3 Sheets-Sheet 1 IN Vii/v70 TORNEY Jan. 15, 1924.

T. KAWAH ELECTRIC SMELTING FURNACE Filed July 23, 1919 3 Sheets-Sheet 2 Jam, 15, 1924. 1,481,210

T. KAWAI ELECTRIC SMELTING FURNACE Filed July 23 1919 3 Sheets-Sheet 5 f IN V/iA TO/g Patented Jan. 15, 1924.

um'rEo STATES PATENT OFFICE.

TOKUJI KAWAI, OF KOKURA, JAPAN.

ELECTRIC SMELTIN G FURNACE Application filed July 23, 1919. Serial No. 312,785.

To all whom it may concem Be it known that I, TOKUJI KAWAI, a subject ofthe Emperor of Japan, and a resident of No. 214 Konya-Machi, Kokura, Empire of Japan, have invented a new and useful Improvement in Electric Smelting Furnaces, of which the following is a specification.

This invention relates to improvements in electric'smelting furnaces, one object being to effect improvements in the construction,

of the furnace; another object being to effect improvements in the means for maintaining an equilibrium of electric intensity at the electrode, to the end that a uniform temperature is maintained in the furnace, and the invention consisting in the construction, combination and arrangement of devices hereinafter described and claimed.

In the accompanying drawings Fig. 1 is a vertical central sectional View of an electric smelting furnace constructed in accordance with one embodiment of my invention. v 1

Fig. 2 is partly a plan and partly a horizontal sectional View of the same.

Fig. 3 is a detail vertical sectional view of the same, showing a portion .of one of the electrodes and, its 'stufling box.

Fig. 4 is an elevation partly in plan of the water supply valve which controls the ver- 7 tical motion of an electrode and associated parts.

In practice the walls of the reducing chamber are lined with magnesite and the bottom of the same is formed of fire brick of superior uality. A plurality of vertically arrange electrodes 5 which are here shown as cylindrical in form are arranged in spaced relation and pass downwardly through openings in the cover 3, which openings are located at points corresponding to vertices of an equilateral triangle, three of such elec-, trodes being here shown, and said electrodes 7 are hence suspended midway between the inner and outer walls of the reducing chamber. The furnace is also provided with feeding passages 6 which are also arranged in spaced relation and intermediate the electrodes, each feeding passage opening at' its lower end through the cover 3 being arranged to discharge into the annular reducing chamber. A discharge port 7 is provided for the said reducing chamber and is arranged directly opposite the center of one of the feeding passages, as shown in Figs.

.1 and 2.

Theannular reduction chamber 4 has its deep portion at the point corresponding to the axis of the electrodes, and the feeding passages are so constructed-that the sloping portion of each of them is oval in cross section, while the upright portion is triangular'in section at the lower part. The delivery port of the valve is smaller than any other part and hence the electrode is enabled to gradually move in the vertical direction, and without vibration.

' When a three-phase alternating current is caused to pass through the electrodes thus constructed, the electric resistance between the electrodes is kept constant; and an approximate equilibrium of electric intensity is maintained. The melting of the material first occurs at points near the electrodes, and then extends to points between the electrodes. The bottom of the annular reducing chamber, corresponding to the electrodes, is concave and the furnace is so constructed that it provides a sufficient depth below the lowest part of the feeding passages, and the molten iron assembles below the electrodes, thus facilitating the melting of the material. Iron has a small electric resistance, and owing to the construction of the annular reduction chamber the electric resistance is hence decreased. Moreover, the molten iron issues from the discharge port at its maximum temperature. 1

A pump cylinder 9, in which an ordinary piston moves along, is provided above each electrode, and a tubular piston rod 10 is fixed at its upper end to the said piston opening to the upper side of the piston, and its lower end to a supporting cap 8 provided at the top of the electrode. Hence the cooling water supplied from a suction pipe 11 communicates, through the piston chamber above the piston and the tubular piston rod 10, to a chamber 12 formed between the supporting cap 8=and the upper end of the electrode. Th cooling water in the chamber 12 is discharged through the pipe 12' attached to the cap 8 and through the pipe 10 attached to the stuffing box 13 which to a tank containing water under sufficient hydraulic pressure to elevate the cylinder piston and then the electrode 5 against their own weightand the water pressure on the piston. A three-way valve ll is provided in the water pipe which connects the suction pipe ll and said water tank, and located on lower elevation than the lower end of the pump cylinder. Fig. 4 shows the operation of said three-way valve 14;. The stem of the valve 14 is fixed to the middle point of any operating lever 15, one end of which is constantly pressed by a spiral spring 16, and which is operated by the iron plunger 18 of an electro-magnet by means of a link 17. The valve 1% is usually kept in such a position that its three passages are all closed, and when electric current passes through the said electromagnet, a set of two passa' cs. one of which leads to the suction pipe 11 the other to the water tank or to the open air. is in communication by means of the operation of the plunger 18, so as to supply water to the lower portion of the pump or discharge it therefrom.

I must now describe the electrical connections of the present system, before the detailed explanation of the hydraulic operation is done.

A main transformer group 19 consists of three transformers in a delta connection; their secondary coils being electrically connected to the electrodes. I A converter 20 is electrically connected with the abov conductor, and its secondary coil is connected with a star connection through a coil 21 of a differential relay. A shunt of the secondary coil of the main transformer is connected with the star connection through a resistance 23, and the coil 21 of the differential relay. An auxiliary transformer 22 serves to introduce a current to the electro-magnet when the relay is operated, so that current is introduced to either a coil 24 or a coil 24, and hence serves to move the iron plunger 18 by means of the operation of the relay according to the condition of the electric current passing through the electrodes. The differential relay employed in this apparatus is so constructed that it is operated by the difference of electric current passing through the coils 2i and 21, which COllSll'uP- tion and operation are similar to those of ordinary relays. When a current of certain phase is caused to decrease by the reason of increase of resistance in the furnace, the terminals 26 and 2? are brought into contact with each other bythe operation of the differential relay, and thereby a. current is introduced to the coil 24: so as to move the iron )lunger 18 to the right hand side (Fig. 4) which causes the operating lever 15 to turn clockwise, so that the water contained below the lower face of the piston in the pump 9 is discharged therefrom, and the electrode starts to come down by its own weight. This results in increasing the current in the furnace until it has attained a certain limit. When the current is increased th terminals 25 and 26 are brought in contact with each other, and thereby the current is introduced to the coil 24 so as to attract the iron plunger 18 to the left hand side (Fig. 4), and hence water is supplied to the lower side of the piston from the water tank. It will be understood that the water tank and the valves, as well as their operating devices are installed a suitable distance from the furnace and one of the valve operating devices should be provided for each valve, the differential relay being preferably fitted adjacent to the valve.

A gate 28 is fitted in the lower portion of each feeding passage 6, and a self closing device is provided in the upper part of each feeding passage. The self-closing device is shown in Fig. 1, and comprises a funnel case 29 which is suspended in the upper part of the feeding passage 6'in such manner that the partof the funnel case of larger diameter is tightly fitted in the supply 'or feedin passage. A conical cover 30 is provide between the part of the funnel case of larger diameter and that of smaller diameter. An inlet cover 32 is fixed to the lower end of a suspension rod 31 passing through the center of the conical cover 30, and the upper end of the suspension rod 31 is provided with a movable ulley 33. The conical cover 30 is suspended in the funnel case 29 by means of a rope 34 which has a definite length and is engaged with a fixed pulley 33 and the movable pulley 33. The weight of the inlet cover 32 is slightly greater than that of the funnel core and the conical cover, so that when material is supplied to the part of funnel case of greater diameter, the funnel case 29 starts to sli down along the supply passage 6, and at t 9 same time the conical cover 30 also begins to come down, and the inlet cover 32 is on the contrary elevated with the movable pulley 33. When the funnel case 29 has been lowered to a certain limit, the conical cover 30 is stopped, and before the supply port is opened. The lower edge of the funnel case is at this moment brought into contact with the inner cover, so that the funnel case is prevented such means.

from descending? further, ply port is not opened. Consequently, the material is deposited in the part of the funnel case of smaller diametenand/when the inlet cover has been opened by its own weight the movable pulley 33 begins to radpart of the furnace supportand the leading pipe 35, thus preventing the furnace .coverfrom overheating'and maintaining its durability. The purified gas is caused to pass through the material in the furnace,

thereby minimizing the oonsiunption of re ducing agent and the electric current, it being understood that an air pump for forcing the gas is installed at asuitable distance from the furnace.

The upper portion of each electrode forms an inverted conic frustum on which a number of copper pieces are attached, and the supporting cap 8 is attached to said copper pieces by screws, thus enabling the supporting cap to introduce the current, and hence electric contact resistance with the electrode is decreased. Moreover, the electrode, is rigidly secured. It should be understood that the plunger rod is. electrically insulated from said supporting cap. It has been heretofore attempted inelectric furnaces to keep the electric resistance constant in several phase between the electrodes by disposing the electrodes at points corresponding to vertices of a triangle but it is well known that the constant resistance has never been attained in such furnaces by According to m invention an adjusting means is provide for the electrodes, and electrically operated means, responsive to variations in resistance is provided to automatically control the operation of the said and hence the sup vertical movement imdepen .lower said rod and said adjusting means, and hence I am enabled to maintain a uniform temperature in the furnace. I also provide means for cooling the electrodes as required, which cooling means is an adjunct of the automatically acting electrode adjusting means.

In addition to the above, my improved smelting furnace is characterized in that the falling sheet of material can appropriately' be compensated by the slope of the supply passages, so that the electrodes may be surrounded in good state by the material to be melted, vibration of the electrodes prevented, the formation of electric arcs prevented; and an electric intensity and the electric oscillation are maintained in a good condition. The gas generated in the furnace is also utilized by means of tighten ing the supply port, andhence the efliciency of the furnace is increased.

Having thus described my invention, I

claim V v 1. An electric smelting furnace having a feeding passage, provided with an inclined portion.- immediately rising from the reducing chamber and a vertical upper portion, a funnel case vertically slidably fitted at the upper end of'the passage, a conical cover I in the funnel case and arran d for limited ently thereof, an inlet cover at'the lower end of the funnel case, a rod connectin and said inlet (woven-and means to raise on covers.

2. In Jan electric smelting furnace, an electrode arranged for vertical adjustment, hydraulically operated means to adjust and said conical cover cool the electrode and including a controlling valve, and electrically operated means, responsive to variations in resistance to automatically operate said valve and hence cause the'hydraulically operated means .to adjust the electrode.

n testimony whereof I aflix my signature in presence of two witnesses.

K. KATO, V A. YASUMUTO. 

